1. Field of the Invention
The present invention relates to an apparatus and a method for synchronizing a Security Association (SA) state in a mobile terminal. More particularly, the present invention relates to a method and an apparatus for allowing a terminal to use a service through a secure network without interruption by immediately re-performing an SA procedure in the case where a server loses SA information of the terminal.
2. Description of the Related Art
Internet Protocol Security (IPSec) is a communication protocol that provides secure communication on the Internet, which is vulnerable to security breaches, and prevents illicit behavior such as wiretapping data by establishing a virtual private circuit via the Internet. Unlike a conventional security technique that provides security while an application layer transmits data, the IPSec protocol provides security while an IP layer transmits data.
The IPSec may be implemented in a terminal near a user. In a conventional method, a terminal implementing the IPSec establishes a tunnel according to the IPSec and transmits a data packet through the tunnel in order to provide a service (for example, an IP Multimedia Subsystem (IMS), Digital Video Broadcasting-Handheld (DVB-H), a Wireless Fidelity (WiFi)-based service, etc.) through a secure network. To use the IPSec, a Security Association (SA) procedure should be performed first. The SA procedure is a procedure that consults between ends about an IPSec protocol operating mode, a code algorithm, a code key communication method, etc. When the SA procedure ends, a terminal and a server may exchange data through a secure port of a tunnel established through the SA procedure.
Through the conventional SA procedure between the terminal and the server, SA information regarding the terminal is stored in a database of the server. However, in the conventional art, if the server loses the SA information of the terminal, the terminal cannot use a service through the secure network. Furthermore, when the SA procedure ends, the terminal operates an SA timer. Accordingly, when the server loses the SA information of the terminal, the terminal cannot use the service until the SA timer expires. In a worst case scenario, this may be one hour and thirty seconds. That is, the terminal must wait until the SA timer expires and then perform the SA procedure again with the server to reestablish the secure service. Also, the terminal must constantly transmit an INVITE message requesting a service to the server during an operating time of the SA timer, which causes a waste of resources due to unnecessary retransmission of a message by the terminal.
Accordingly there is a need for an apparatus and a method for synchronizing an SA state in the case where SA information of the mobile communication terminal is lost.